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United States Patent |
6,076,407
|
Levesque
,   et al.
|
June 20, 2000
|
Pipe inspection probe
Abstract
A probe for inspecting the inside of a large diameter, substantially
vertical, limited access pipe. The probe includes an elongated probe
housing having a series of flexible joint along its length to permit the
probe to be positioned within the pipe. A plurality of radially extendable
guide arms are attached to the lower end of the probe housing for
positioning the probe within the pipe and, in the preferred embodiment, a
stabilizer weight is attached to the elongated housing adjacent to the
guide arms for preventing unstable movement of the probe much like a tail
on a kite. In the preferred embodiment, the probe further includes a
rotational drive for rotating the plurality of radially extendable guide
arms with respect to the elongated housing. In addition, sensors are
located on the ends of each guide arm to permit the inside surface of the
pipe to be more completely inspected for defects. Also, an axial drive
moves the probe along the length of the pipe and is controlled by an
output from the drive for rotating the plurality of radially extendable
guide arms with respect to the elongated housing.
Inventors:
|
Levesque; Michael Paul (Lynchburg, VA);
Sheppard, II; John Paul (Lynchburg, VA);
Ales; Matthew Wayne (Amherst, VA)
|
Assignee:
|
Framatome Technologies, Inc. (Lynchburg, VA)
|
Appl. No.:
|
079578 |
Filed:
|
May 15, 1998 |
Current U.S. Class: |
73/623; 73/866.5; 324/220 |
Intern'l Class: |
G01N 029/24 |
Field of Search: |
73/866.5,623,40.5 R,40.5 A,865.8
324/220,221
|
References Cited
U.S. Patent Documents
3862578 | Jan., 1975 | Schluter | 73/866.
|
4304134 | Dec., 1981 | Rouse et al. | 324/220.
|
4581927 | Apr., 1986 | Johnson | 73/152.
|
4820982 | Apr., 1989 | Aubert | 324/300.
|
4843896 | Jul., 1989 | Napeloni et al. | 73/866.
|
5105881 | Apr., 1992 | Thoms et al. | 73/784.
|
5195392 | Mar., 1993 | Moore et al. | 73/866.
|
5520245 | May., 1996 | Estes | 73/152.
|
5565633 | Oct., 1996 | Wernicke | 73/866.
|
5760306 | Jun., 1998 | Wyatt, III et al. | 73/623.
|
Primary Examiner: Williams; Hezron
Assistant Examiner: Fayyaz; Nashmiya
Attorney, Agent or Firm: Rhodes & Mason, PLLC
Claims
We claim:
1. A probe for inspecting the inside of a large diameter, substantially
vertical pipe, said probe comprising:
(a) an elongated probe housing adapted to be positioned within said pipe;
(b) a plurality of radially extendable guide arms attached adjacent to a
distal end of said probe housing for positioning said probe within said
pipe; and
(c) a stabilizer weight vertically suspended from said distal end of said
elongated housing for preventing unstable movement of said probe, wherein
said stabilizer weight is attached to said elongated housing by a flexible
joint.
2. The probe according to claim 1, wherein said stabilizer weight is an
elongated cylinder having an outer diameter substantially equal to or less
than the diameter of said elongated housing.
3. The probe according to claim 1, wherein each of said guide arms has an
outer end and a contact point disposed thereon, and wherein the center of
gravity of said weight is below a plane determined by the contact points
of the outer ends of the guide arms, thereby maintaining central and axial
alignment of said probe.
4. The probe according to claim 1, wherein said flexible joint permits
axial bending of about .+-.5.degree..
5. The probe according to claim 1, wherein said flexible joint is a
universal joint.
6. A probe for inspecting the inside of a large diameter, substantially
vertical, limited access pipe, said probe comprising:
(a) an elongated probe housing having at least one flexible joint to permit
said probe to be positioned within said pipe;
(b) a plurality of radially extendable guide arms attached adjacent to a
distal end of said probe housing for positioning said probe within said
pipe;
(c) a stabilizer weight vertically suspended from said distal end of said
elongated housing adjacent to said guide arms for preventing unstable
movement of said probe, wherein said stabilizer weight is an elongated
cylinder having an outer diameter substantially equal to or less than the
diameter of said elongated housing; and
(d) a rotational drive means for rotating said plurality of radially
extendable guide arms with respect to said elongated housing and an axial
drive means for moving said probe along the length of said pipe, wherein
said axial drive means for moving said probe along the length of said pipe
is controlled by an output from said means for rotating said plurality of
radially extendable guide arms with respect to said elongated housing.
7. A probe for inspecting the inside of a large diameter, substantially
vertical, limited access pipe, said probe comprising:
(a) an elongated probe housing having at least one flexible joint to permit
said probe to be positioned within said pipe;
(b) a plurality of radially extendable guide arms attached adjacent to a
distal end of said probe housing for positioning said probe within said
pipe, wherein said plurality of radially extendable guide arms each
includes an outer arm attached at one end to said probe housing, a linear
actuator and a link arm attached to said actuator and said outer arm for
extending said guide arms; and
(c) a stabilizer weight vertically suspended from said distal end of said
elongated housing adjacent to said guide arms for preventing unstable
movement of said probe.
8. The probe according to claim 7, wherein at least one of said plurality
of radially extendable guide arms includes a sensor assembly for detecting
a defect in said pipe.
9. The probe according to claim 8, wherein said sensor assembly is
pivotable with respect to the ends of said plurality of guide arms
adjacent to the inside surface of said pipe.
10. The probe according to claim 8, wherein said sensor assembly includes
an NDE sensor.
11. The probe according to claim 10, wherein said NDE sensor is an
ultrasonic crack detector.
12. The probe according to claim 7, wherein said link arms are attached to
said linear actuators by shear pins to permit removal of said probe in the
event of a failure wherein said plurality of radially extendable guide
arms are stuck in an open position.
13. The probe according to claim 12, wherein said shear pins are captured
to prevent loose parts in the event of a failure.
14. The probe according to claim 7, wherein each said actuator is a
pneumatic cylinder and pull rod.
15. A probe for inspecting the inside of a large diameter, substantially
vertical, limited access pipe, said probe comprising:
(a) an elongated probe housing having at least one flexible joint to permit
said probe to be positioned within said pipe;
(b) a plurality of radially extendable guide arms attached adjacent to a
distal end of said probe housing for positioning said probe within said
pipe; and
(c) a stabilizer weight vertically suspended from said distal end of said
elongated housing adjacent to said guide arms for preventing unstable
movement of said probe, wherein said stabilizer weight is attached to said
elongated housing by said flexible joint.
16. The probe according to claim 15, wherein each of said guide arms has an
outer end and a contact point disposed thereon, and wherein the center of
gravity of said weight is below a plane determined by the contact points
of the outer ends of the guide arms, thereby maintaining central and axial
alignment of said probe.
17. The probe according to claim 15, wherein said flexible joint is a
universal joint.
18. The probe according to claim 15, wherein said flexible joint permits
axial bending of about .+-.5.degree..
19. The probe according to claim 15, wherein said stabilizer weight is an
elongated cylinder having an outer diameter substantially equal to or less
than the diameter of said elongated housing.
20. The probe according to claim 15, wherein said flexible joint is a
universal joint.
21. The probe according to claim 15, wherein said flexible joint permits
axial bending of about .+-.5.degree..
22. The probe according to claim 15, further including rotational drive
means for rotating said plurality of radially extendable guide arms with
respect to said elongated housing.
23. The probe according to claim 22, wherein said rotational drive means is
located between said elongated housing and said plurality of radially
extendable guide arms to reduce wind-up error.
24. The probe according to claim 22, wherein said rotational drive means is
a brushless DC servomotor.
25. The probe according to claim 22, further including axial drive means
for moving said probe along the length of said pipe.
26. The probe according to claim 25, wherein said axial drive means for
moving said probe along the length of said pipe is controlled by an output
from said means for rotating said plurality of radially extendable guide
arms with respect to said elongated housing.
27. The probe according to claim 15, wherein said plurality of radially
extendable guide arms attached to the lower end of said probe housing for
positioning said probe within said pipe each includes an outer arm
attached at one end to said probe housing, a linear actuator and a link
arm attached to said actuator and said outer arm for extending said guide
arms.
28. The probe according to claim 27, wherein at least one of said plurality
of radially extendable guide arms includes a sensor assembly for detecting
a defect in said pipe.
29. The probe according to claim 28, wherein said sensor assembly is
pivotable with respect to the end of said at least on of said plurality of
guide arms adjacent to the inside surface of said pipe.
30. The probe according to claim 28, wherein said sensor assembly includes
an NDE sensor.
31. The probe according to claim 30, wherein said NDE sensor is an
ultrasonic crack detector.
32. The probe according to claim 27, wherein said link arms are attached to
said linear actuators by shear pins to permit removal of said probe in the
event of a failure wherein said plurality of radially extendable guide
arms are stuck in an open position.
33. The probe according to claim 32, wherein said shear pins are captured
to prevent loose parts in the event of a failure.
34. The probe according to claim 27, wherein each said actuator is a
pneumatic cylinder and pull rod.
Description
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates generally to an apparatus for inspecting the
interior of generally vertical conduits or piping and, more particularly,
to an apparatus for detecting and determining both the axial and angular
positions of detected defects in the variable diameter jet pump diffusers
such as found in a boiling water (BWR) nuclear reactors.
(2) Description of the Prior Art
Coolant piping in a BWR must be periodically inspected to detect cracking
due to either intergranular Stress Corrosion Cracking (IGSCC) or fatigue
in the tubing walls, so that these areas can be repaired to prevent
leakage. Usually detection is performed externally since there was no way
to insert an inspection probe into the jet pump diffuser assembly
consisting of the jet pump mixers, diffuser and adapters. This is because
the access opening to the internal tubing is limited while the inside
diameter of the piping may vary over its length from between about 3 to 22
inches. However, because of supports and other attachments, not every
portion of the piping can be inspected externally.
Probes have been developed to detect and located defects inside the much
smaller steam generator tubing which has an inside diameter of about 3/4
inch. These probes may include a rotatable probe head positioned at the
end of a tubular carrier through which electrical wiring connects the
drive means and detector of the probe head to an external power source and
controls. The probe head includes a detector, e.g., an ultrasonic
detector, an eddy current detector, or both, which measures changes in
wall conditions.
The axial position of the wall defect can be determined by measuring the
distance that the probe head has been inserted into the tubing. In
addition, encoders have been used to determine the angular position of the
defect which is helpful in properly correcting the defect. One example of
such a probe for steam generator tubing is disclosed in U.S. Pat. No.
5,760,306 (to be issued Jun. 2, 1998), issued to Wyatt, III et al., which
is hereby incorporated by reference in its entirety. However these probes
could not be used for the much larger and variable diameter jet pump
diffuser assembly piping which varies between about 3 and 22 inches over
its length.
Thus, there remains a need for a new and improved apparatus for detecting
and determining both the axial and angular positions of detected defects
in the inside of a pipe while, at the same time, is able to conform to
large, variable diameter jet pump diffusers such as found in a BWR nuclear
reactors.
SUMMARY OF THE INVENTION
The present invention is directed to a probe for inspecting the inside of a
large diameter, substantially vertical, limited access pipe. The probe
includes an elongated probe housing having a series of flexible joint
along its length to permit the probe to be positioned within the pipe.
Each of the flexible joints permits axially bending of about .+-.5.degree.
each to permit the probe to turn into a limited access inspection port.
A plurality of radially extendable guide arms are attached to the lower end
of the probe housing for positioning the probe within the pipe and, in the
preferred embodiment, a stabilizer weight is attached to the elongated
housing adjacent to the guide arms for preventing unstable movement of the
probe. The center of gravity of the weight is below the plane determined
by the contact points between the outer ends of the guide arms and the
pipe wall thereby maintaining axial alignment of the probe and causing the
ends of the guide arms to move in a true helical pattern as the probe
moves through the pipe. In addition, the stabilizer weight is attached to
the elongated housing by a flexible joint to further aid in access to
difficult to reach inspection ports.
In the preferred embodiment, the probe further includes a rotational drive
for rotating the plurality of radially extendable guide arms with respect
to the elongated housing. In addition, sensors may be located on the ends
of each guide arm to permit the inside surface of the pipe to be more
completely inspected for defects. Also, an axial drive moves the probe
along the length of the pipe and is controlled by an output from the drive
for rotating the plurality of radially extendable guide arms with respect
to the elongated housing.
Accordingly, one aspect of the present invention is to provide a probe for
inspecting the inside of a large diameter, substantially vertical pipe.
The probe including: (a) an elongated probe housing adapted to be
positioned within the pipe; and (b) a plurality of radially extendable
guide arms attached to the lower end of the probe housing for positioning
the probe within the pipe.
Another aspect of the present invention is to provide a probe for
inspecting the inside of a large diameter, substantially vertical, limited
access pipe. The probe includes: (a) an elongated probe housing having at
least one flexible joint along its length to permit the probe to be
positioned within the pipe; and (b) a plurality of radially extendable
guide arms attached to the lower end of the probe housing for positioning
the probe within the pipe.
Still another aspect of the present invention is to provide a probe for
inspecting the inside of a large diameter, substantially vertical, limited
access pipe. The probe includes: (a) an elongated probe housing having at
least one flexible joint along its length to permit the probe to be
positioned within the pipe; (b) a plurality of radially extendable guide
arms attached to the lower end of the probe housing for positioning the
probe within the pipe; and (c) a stabilizer weight attached to the
elongated housing adjacent to the guide arms for preventing unstable
movement of the probe.
These and other aspects of the present invention will become apparent to
those skilled in the art after a reading of the following description of
the preferred embodiment when considered with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a probe constructed according to the
present invention having the guide arms in a radially extended position
and having portions of the outer housing cut-away for detail into the
interior of the invention;
FIG. 2 is a cut-away view of the guide arms of the probe illustrating the
guide arms in a closed retracted position;
FIG. 3 is a cut-away view of the probe having the guide arms radially
extended along the inside diameter of a pipe;
FIG. 4 is a cross-sectional view of the probe being inserted into a pipe;
FIG. 5 is a perspective view of the probe driver assembly; and
FIG. 6 is an exploded view of the connector attaching the pull rod and link
arm.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the following description, like reference characters designate like or
corresponding parts throughout the several views. Also in the following
description, it is to be understood that such terms as "forward,"
"rearward," "left," "right," "upwardly," "downwardly," and the like are
words of convenience and are not to be construed as limiting terms.
Referring now to the drawings in general and FIG. 1 in particular, it will
be understood that the illustrations are for the purpose of describing a
preferred embodiment of the invention and are not intended to limit the
invention thereto. The invention is a remotely controlled tool used for
the ultrasonic inspection of the welds in the jet pump diffusers of a
boiling water reactor. As best seen in FIG. 1, a probe for inspecting a
vertically oriented, variable inside diameter pipe, generally designated
10, is shown constructed according to the present invention. The probe 10
includes a probe head 12 having an elongated housing 13 and a plurality of
guide arms 16. The elongated housing 13 includes a plurality of flexible
joints 20 spaced along the length to allow the probe to be inserted and
moved through various pipe configurations. A rotational drive motor 22
rotates the guide arms 16 along the inside diameter of the pipe and an
axial drive motor 44 located upstream of the probe provides for movement
of the probe along the pipe length. In the preferred embodiment, the probe
10 further includes a weight 14 attached to the lower end of the probe
head 12 for maintaining the vertical orientation of the probe in the
interior of the pipe.
The elongated housing 13 functions to protect the drive elements from
damage during use. In a preferred embodiment, the housing 13 is
constructed of high strength aluminum or stainless steel. The housing 13
may include removable sections 46 to provide access to specific interior
sections of the probe head and are preferably placed over areas that may
require repair or calibration.
A sheath 50 extends between the probe head 12 and a probe driver assembly
44. The sheath 50 is torsionally rigid yet flexible and acts as a
protective shroud for the conductors and pneumatic lines that extend to
the probe head. The sheath 50 further functions as the medium for driving
the tool axially within the piping. The probe driver assembly 44 is
located at the upper-most level of the probe outside the jet pump diffuser
to provide for axial movement of the probe along the length of the pipe.
The probe driver assembly includes a takeup reel 52 and a set of pinch
wheels 54 to lower and raise the probe head along the length of the pipe
as illustrated in FIG. 5. In a preferred embodiment, the pinch wheels are
driven by a DC servomotor. The probe assembly further includes a means for
determining the axial position of the probe within the piping, such as a
resolver within an axial encoder. In one embodiment, axial encoding is
provided by a separate unit connected to the probe driver and guide tube.
The flexible joints 20 located along the probe length allow the probe to be
bent and manipulated to provide for installation and movement throughout a
variety of pipe configurations as illustrated in FIG. 4. In the preferred
embodiment, three joints in series, each movable about .+-.5.degree.,
allow the probe housing 12 to be bent sufficiently, over a total range of
about 30.degree., to allow insertion of the probe into the jet pump
diffuser. It is understood that the present invention contemplates any
number of flexible joints along the probe length depending upon the needs
of the hardware being inspected.
The rotational drive motor 22 is positioned within the probe head 12 to
rotate the guide arms 16. Preferably, the rotational drive 22 is
positioned in proximity to the guide arms 16 to prevent "wind up" which
occurs when a length of sheath 50 is rotated causing twist along the
sheath length which may cause inaccuracies in the measurements of the
inspection. By rotating a short, rigid length of probe, the amount of
"wind up" is reduced resulting in greater inspection accuracy. In one
preferred embodiment, the rotational drive 22 is a brushless DC motor with
Hall-effect commutation for circumferential encoding. In a preferred
embodiment, an encoder communicates between the axial and rotational
drives to control the speeds of the axial movement of the probe head
relative to the rotational movement during the inspection process such
that the axial drive is slave to the rotational drive.
A plurality of radially extendable guide arms 16 are placed on the probe
head. In a preferred embodiment, three guide arms are spaced about the
probe as illustrated in FIG. 1. Each of the guide arms 16 includes an
outer arm 24 and a link arm 26. The outer arms 24 are positionable to
extend across the inside diameter of a pipe ranging from about 3 to 22
inches and, possibly, having a tapered diameter. The outer arm includes a
first end 33 that is pivotally mounted to the probe head and a second end
35 may be equipped with sensor assemblies 32.
A linear actuator 30 including a pneumatic cylinder and the pull rod 51
expands and contracts the guide arms 16 during the inspection process via
the link arms 26 that extend between the pull rod 51 and the guide arms.
The pull rod 51 is axially pulled and pushed along with the rotational
drive 22 by the pneumatic cylinder thereby causing the link arms to push
and pull the guide arms opened and closed. By way of example, the guide
arms are in a retracted position as illustrated in FIG. 2. To extend the
guide arms as illustrated in FIG. 1, the pull rod is axially pulled
thereby causing the link arms 26 to push open the guide arms. The pull rod
51 is pulled a greater distance to extend the guide arms to a fully
extended position or a lesser amount to extend the guide arms a smaller
distance depending upon the inside diameter of the piping. The pneumatic
cylinder acts to ensure that the guide arms remain in contact with inner
diameter of the piping during the inspection process.
The link arm 26 is attached to the pull rod 51 by a fastener 60 as
illustrated in FIG. 6. The fastener 60 includes a shear plane 62
positioned between the link arm 26 and pull rod 51 such that in the event
that the guide arms are stuck in an open position, the force of probe
drive 44 pulling the probe head will cause the shear planes to fail,
thereby allowing the guide arms to collapse. After the shear plane fails,
probe driver assembly 44 axially pulling the probe head out of the piping
will cause the guide arms to retract as the guide arms are no longer being
kept open. In a preferred embodiment, the angle a between the guide arms
16 and probe head 12 will be about less than or equal to 90 degrees to
provide for the axial movement of the probe to close the guide arms. The
connection between the guide arms 16 and the pull rod 51 also provides for
no particles to break off and escape into the piping as the pieces of the
connector are captured.
The sensor assemblies 32 function to detect and length size relevant flaws
oriented parallel to the weld and may initiate from either the inner or
outer diameter of the piping. The scanning technique involves placement of
the sensor assemblies 32 on the inside diameter of the piping and is
achieved by pivotally connecting the sensors to the outer arms 24 at
pivots 36 as illustrated in FIG. 1.
The sensor assemblies may vary depending upon the specific parameters of
the inspection process. In one i embodiment, the sensor assemblies include
two circumferential flaw detecting transducers positioned on the first
outer arm, one transducer for circumferential flaw detecting on the second
outer arm, and two axial flaw detecting transducers on the third outer
arm. Preferably, the transducers use 60 degree refracted shear waves
directed in both the upward and downward and the clockwise and
counter-clockwise directions so that the sound beams are aimed essentially
both normal and parallel to the weld axis. In the preferred embodiment,
the housing holding the transducers also include small guide wheel that
ride on the inside surface of the piping to reduce friction.
A sensor seater 46 is positioned on the probe head to ensure the sensor
assemblies 32 are properly seated when the guide arms 16 are retracted as
illustrated in FIG. 2. As the guide arms 16 are retracted towards the
central axis of the probe head, the sensor assemblies contact the sensor
seater 46 causing the sensors to pivot thus allowing them to seat within
the probe head.
A weight 14 is positioned downstream of the retracted guide arms position.
The weight provides a center of gravity for the probe below the contact
point plane of the guide arms where the sensor assemblies contact the
inside diameter of the pipe. The weight 14 provides for the probe to
maintain central and axial position within the pipe to ensure for more
accurate inspection results. Preferably, the weight has a cylindrical
shape having less than or about the same diameter of the housing to permit
insertion into the same size access openings that the probe body can pass
through.
In operation, the guide arms 16 are placed in the full retracted position
as illustrated in FIG. 2. The probe is then delivered through a series of
handling poles 70 into the piping through the top of the jet pump inlet
mixer nozzle 72 as illustrated in FIG. 5. The handling poles 70 provide an
in-line calibration standard such that the probe does not have to be
removed from the reactor vessel in order to perform a calibration. The
flexible joints 20 allow the otherwise rigid probe head 12 to be inserted
into the piping. The probe is lowered into the piping weight end 14 first.
The probe driver assembly 44 pays out the sheath to allow the probe to
descend the proper distance. When the distance is in the correct axial
location, the guide arms 16 are extended to allow the sensor assemblies 32
to contact the inside diameter of the piping as illustrated in FIG. 3.
The probe driver assembly 44 moves the probe head 12 through the desired
axial length of the piping as the rotational drive 22 rotates the guide
arms. The probe moves along the piping length to helically scan the area
of interest. When the inspection process is complete, the guide arms are
retracted to the closed position, and the probe is pulled from the piping.
It will be understood that the present invention provides for a remotely
controlled tool used for the ultrasonic inspection of the welds in a jet
pump mixer, diffuser, tail pipe, and adapter of a boiling water reactor.
The invention is capable of inspecting all the welds in the adapter, all
of the welds in the tail pipe region, all the welds in the diffuser, and
some of the welds in the mixer region. It will also be understood that the
pitch of the sensor assemblies can be adjusted.
Certain modifications and improvements will occur to those skilled in the
art upon a reading of the foregoing description. By way of example, the
air cylinder could be a piston within the housing using the rotary drive
as the piston body. This would allow greater force to open the guide arms.
Also, larger wheels could be incorporated into the transducer housing to
further reduce friction. This could be coupled with spring loaded
transducers to maintain transducer contact with the pipe wall. Also, the
universal joints could be modular to allow further ease in assembly and
repair. It should be understood that all such modifications and
improvements have been deleted herein for the sake of conciseness and
readability but are properly within the scope of the following claims.
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